The present invention relates generally to methods and apparatus for providing healthcare. More specifically, the present invention relates to methods and apparatus for treating patients via dialysis procedures.
Dialysis provides a method for supplementing or replacing renal function in certain patients. Dialysis is the process of separating elements in a solution by diffusion across a semipermeable membrane (diffusive solute transport) down a concentration gradient. Principally, hemodialysis and peritoneal dialysis are utilized. Although dialysis provides in many cases life saving therapy, there are health issues that must be addressed in such patients.
In a typical hemodialysis system, blood is removed from the patient and pumped to a dialysis machine including a membrane unit. The membrane unit dialyzes the blood which is then returned to the patient through tubing. Hemodialysis machines may be used at a health facility or in the patient's home. The machine attaches the patient through an extracorporeal circuit of blood tubing to a dialyzer having a pair of chambers separated by a thin semi-permeable membrane. The patient's blood is circulated through one of the chambers. The hemodialysis machine maintains a constant flow of a dialysate through the second chamber. Excess water from the blood is removed by ultrafiltration through the membrane and carried out by the dialysate to drain.
A typical hemodialysis machine provides a pair of hoses which connect to the dialyzer and includes a source of incoming water, a heat exchanger and heater for bringing the water to a required temperature, a source of a dialysate concentrate or concentrates which are introduced into the water in a predetermined concentration and necessary pumps, pressure regulators, a deaerator, flow controllers and regulators. In an acetate dialysis system, only one concentrate is utilized, while in the more common bicarbonate dialysis systems, two concentrates, acid and bicarbonate are utilized.
The dialysate delivery system mixes water, generally purified by reverse osmosis or deionization, with an electrolyte concentration so that it approximates the chemical composition of ECF, warms the blood to body temperature, and checks the conductivity to ensure it is isotonic to the patient's blood. A number of commercially available machines are used to administer hemodialysis. Two such systems include the SPS 550 Delivery System and SPS 1550 Delivery System marketed by Baxter Healthcare, Deerfield, Ill.
Membrane units (dialyzers) come in different sizes with differing surface areas, clearance characteristics, and hydraulic coefficients for ultrafiltration. Instructions generally are given with respect to the specifications by the manufacturer. Usually hemodialysis treatments take three to five hours. Most patients with chronic renal failure require three weekly hemodialysis treatments to maintain a state of well being.
One of the possible complications of hemodialysis is hypotension. This is usually due to a reduced blood volume consequent to fluid removable by ultrafiltration and the patient's inability to physiologically compensate for the reduced blood volume.
Under current practice, habitually, hypotensive dialysis patients are given hypertonic saline prophylactically via sterile injections to recruit fluid from the extravascular space to stabilize blood pressure. It is also common to give hypotensive dialysis patients hypertonic saline as a first recourse when hypotension is noted.
Typically, most hemodialysis units monitor, every half hour, the blood pressure of dialysis patients. When blood pressure begins to drop, a hypertonic saline solution is then administered. In other cases, isotonic saline is given, although the patients' weight loss goals must be increased to make up for the additional volume.
All of these procedures require that a nurse inject saline into a blood line to the patient. This requires that the nurse draw the saline into a syringe and inject same at a slow, but sufficient, rate. Unfortunately, demands of the dialysis unit may require the nurse to administer the bolus of saline more quickly than desired. This can result in adverse patient symptoms, such as an accelerated heart rate, sweating, and a burning sensation.
An additional issue raised by the current procedures is the labor intensiveness of the procedure. Blood pressures must be taken at regular intervals. Depending on the number of patients in a unit, the burdens on the nurses can be quite great. These burdens may prevent a nurse from delivering saline to a specific patient at the first onset of symptoms of hypotension.
There is therefore a need for an improved method and apparatus for preventing hypotension in hemodialysis patients.